The present invention relates to a magnetic recording/reproducing apparatus in which adjustment of what may be called X-distance of an Audio/Control (A/C) head, to be described hereinafter, is unnecessary.
In a conventional magnetic recording/reproducing apparatus of rotating head type, a rotating head scans video tracks of a magnetic tape and records video signals thereonto. During a recording, control pulses containing position information for recording tracks are recorded onto a lower track of the tape, and audio signals onto an upper track. Video tracks are slanted with respect to the direction of the tape advancing at a constant rate.
FIG. 1 shows a recording pattern diagram of a magnetic tape for a conventional magnetic recording/reproducing device such as a VHS-type video tape recorder (VTR). When video signals are reproduced from a VHS-type magnetic tape, the VTR's internal drum and capstan servos operate in response to control pulses recorded onto the tape. Without the control pulses, VTR's rotating head cannot precisely track the tape's recordings.
An accurate reading of the control pulses depends on the above-mentioned X-distance of an A/C head, shown in FIG. 2A as the tape length from the falling edge of tape loaded drum 10 (i.e., from the position of the CH-2 head) to the centerline of A/C head 11. The X-distance, also shown in FIG. 1, is regulated to be about 79.244 mm so that control pulses will occur at 6.5 H.+-.0.5 H off from a rising edge of vertical synchronizing signal recorded on the CH-1 track. One unit of H is equal to 63.5 microseconds.
In order to control X-distance, as shown in FIG. 2A, A/C head 11 is secured to A/C head base 17, which is mounted to A/C head base holder 13 by azimuth adjusting screws 14 and 15 and tilt adjust screw 16. A/C head base 17 can be adjusted vertically and transversely. Furthermore, A/C head base holder 13 is supported by rotating shaft 12. Because the holder 13 can rotate about shaft 12, adjusting the height of a cone screw 18 moves holder 13 in transverse direction. If cone screw 18 rotates clockwise, then head of screw 18 will move down and an inclined surface underneath the head will push holder 13 closer to the CH-2 head. This will shorten X-distance of A/C head 11. Conversely, rotating screw 18 counter-clockwise will lengthen X-distance.
The above-mentioned X-distance adjusting design is complex and causes difficulty in constructing small VTR decks. In addition, VTR decks built in accordance with the above design require complex tune-ups.